Market share is never the final determinant of market power. It is used as a screen for further investigation and/or to shift the burden of proof. So, for example, an HHI (Herfindahl Hirschman Index) greater than 1700 or 1800 is triggers anti-trust investigations by the US government in the case of mergers and acquisitions. In the case of determining significant market power in telecom regulation (LIRNEasia is quite skeptical about the value of this approach in developing countries), market shares of around 35-45 percent shift the burden on the operator to prove that it does not have market power (the ability to set and maintain prices in simple language). But in Bangladesh 20 percent market share is the magic number.